Stainless steel with a high boron content

ABSTRACT

A STAINLESS STEEL COMPRISING FROM 20 TO 30% BY WEIGHT CHROMIUM, UP TO 5% NICKEL AND FROM 2 TO 6% BORON WHICH CAN BE WORKED.

United States Patent Oflice 3,736,128 Patented May 29, 1973 3,736,128 STAINLESS STEEL WITH A HIGH BORON CONTENT Jean-Jacques de Cadenet, Ugine, and Andr Gueussier chromium in the matrix may even drop below 10%, which seriously impairs the corrosion resistance of the steels.

According to this invention, there are provided stainless steels with a high boron content which steels do not have reduced corrosion resistance and which can be forged.

and Roland Tricot Albertville France assignors to Pechtney U gin e Kulflmann, Partg France T1he steels of the mventron have the following general No Drawing. Continuation-impart of application Ser. No. we ysls- 780,551, Dec. 2, 1968. This application June 4, 1971, Carbon (C) Up to Ser. No. 150 237 1 Int- CL czzc 39/14 Chromium (Cr) Frgr61%about 20 to about 75-126 3 Clam Nickel (Ni) Up to 5%, preferably only up to 1%. ABSTRACT OF THE DISCLOSURE Mangemese (Mn) Up to A stainless steel comprising from 20 to 30% by weight 5 0 (51) Up to 2%. chromium, up to 5% nickel and from 2 to 6% boron BOTOII m a Pt'ZtO about 6%. which can be worked. Iron (Fe) and impurities The remainder.

Steels according to this invention are characterized by RELATED APPLICATIONS borides dispersed in a metallic matrix. Preferably, the matrix comprises more than 11% by weight, chromium. Thls 15 eentmuatlonqmpare of appheatlol} N The invention pertains to steels fabricated in any man- 780,55l, filed Dec. 2, 1968, havlng the same title, WhlCh her, for example, east or Worked (rolled, forged or claimed priority to French patent application No. PV drawn) e filed Bee 7' In contrast to the conventional high boron stainless Stamless eteels Wlth a hlgh Peron eentent e used In steels derived from the 18Cr-10Ni type steels, the steels the nuclear mdnstry as protection against radlation. Such of the instant invention have the following advantages. steels are effecttve because boron presents alarge absorp- AS Shown by tests made by the applicants they are very cross Peetlen, rartlcularly eapturmg P readily forgeable. Pieces of steel made in accordance with Moreover, in many lnstances 1t is desirable to use stalnthiS invention and containing 34% boron have been less steel as chemically corrosive environments will not forged WherettS thiS operation has been impossible for eause rapld elestfuetlon of the metal' In P Past steels steels having the same boron content but derived from used aPPl1eat,1ns where e were sebleeted to both the 18Cr-l0Ni type stainless steels. Like the steels having ehemleal eorreslen and radlatlen COIPPHSCd about 18% a high boron content and derived from the conventional ehremufm and 10% e or eempnsed aeout the Same 18Cr-10Ni type steels, the steels of this invention are Prepomens of ehrofmum and mekel to Whleh a Proper 35 formed of borides dispersed in a metallic matrix, but here P of boron rangmg from 2% to 4 or even 5% by the allotment of chromium between these two constituwelght was added' ents is such that the metallic matrix remains relatively Such Steels have drawbaeks- They very dlffieult to unoxidizable. And finally, the steels of the invention are forge due to great amount of bendes that e less costly than the steels previously used for the same tain. In practlce they are not forgeable when the1r boron 40 purpeses content exceeds 2%. (This application relates to forgeable By way of comparison, Table I gives the overall 1 Steels containing more than 2% boron) Furthel'nforea ysis, composition of dispersed borides and composition these steels have reduced corrosion resistance. Thls 15 f t lli t i for ix known steels (Examples 1 to because the borides which are dispersed in the metallic 6) T bl II gives th a e data for three steels made matrix become very rich in chromium. Thus, the chroaccording to the teachings of this invention (Examples 7 mium in the metallic matrix is reduced. The content of to 9).

TABLE 1'.

Example 1 2 3 4 5 6 Overall analysis:

Traces Traces Traces Traces Traces Traces 0.2 1.8 6.5 0.1 0.1 0.1 1. 0 1. 0 0. 9 1. 45 2.1 1. 0 45 47 45. 5 37. 6 41. 9 53. 0

In Tables I and II only the alloying elements are given. The remainder of the overall analysis and composition of the metallic matrices are, of course, iron and impurities. The remainder of the boride compositions is boron.

Table I establishes that the chromium content of the metallic matrix of Examples 1 to 6 reaches a maximum of about On the other hand, Table II establishes that the chromium content of the matrices of Examples 7 to 9 according to this invention are always higher than 11%. Hence, these steels remain relatively chemically resistant or unoxidizable.

Having thus described our invention with the detail and particularly as required by the patent laws, what is desired protected by Letters Patent is set forth in the following claims.

We claim:

1. Forgeable, corrosion-resistant steels consisting essentially of up to 0.2% by weight carbon, from about 20 to 30% chromium, up to 5% nickel, up to 3% manganese, up to 2% silicon, from 2.0 to 6% boron, the remainder comprising iron and impurities, said boron being present as borides dispersed in a metallic matrix analyzing greater than about 11% by weight chromium.

2. Steels according to claim 1 comprising up to 1% nickel.

3. Nuclear radiation shields comprising forgeable, corrosion-resistant steels consisting essentially of up to 0.2% by weight carbon, from about 20 to 30% chromium, up to 5% nickel, up to 3% manganese, up to 2% silicon, from 2.0 to 6% boron, the remainder comprising iron and impurities, said boron being present as borides dispersed in a metallic matrix analyzing greater than about 11% by weight chromium.

References Cited UNITED STATES PATENTS 2,432,616 12/1947 Franks -128 F 2,479,097 8/1949 Buchanan 75128 F 2,905,577 9/1959 Harris 75126 P HYLAND BIZOT, Primary Examiner US. Cl. X.R. 

